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G'day, while trying to change the timing belt i've noticed that when the L.H. Camshaft sprocket and the Crankshaft sprocket are lined up the R.H. Camshaft sprocket is 1/2 a tooth out away from the center of the engine. As well as that when I crank it over by hand back to the timing marks the belt ends up 1 tooth out each time I go to line them up. Any suggestions or advice would be much appreciated. Cheer's - George
 

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no guarantees.....



Between passenger cam gear (R3) and Driver side (L3) cam; 40 teeth
Between Driver side cam (L3) and crank sprocket gear: 43 teeth
Between the Crank sprocket gear and back again to passenger cam gear; 50 teeth ........ Total teeth on the belt are 133 teeth.


PARTS............


timing belt...OEM
tensioner and stud...OEM
water pump
thermostat...OEM...Robert Shaw...BeckArnley...no Stant?
small 90* hose
short 4 inch hose from thermostat to suction tube
both upper radiator hoses
lower radiator hose
new clamps?
crank seal
crank seal plate
cam seals
CHTS and harness
new crank gear (worn?)
new OEM key...these are hard to find aftermarket?



Timing belt change . . .

Use of this "method" assumes that your car is running OK before you change the belt. If the belt has broken or sheared some teeth, you'll need to line it up from scratch.

* You also should use the any other info on the Z31 site, other sites, and in the Haynes or other manuals. If there is any disagreement, just THINK about it a while.

* The first thing I'd do BEFORE starting this job would be to start the car up from cold and let it warm up to just the point that the temp gauge hits it's normal operating temp....then shut it off. Take a flashlight and carefully look at the top side of the motor between the valve covers for any slight coolant leaks you might see...these will likely show up as some slight dampness only, usually towards the front...you'll need to stop these leaks during this job.

*No need to remove the valve covers or the spark plugs, or to rotate the engine to seat the belt, or use a feeler gauge, and I'd recommend discarding the tensioner spring, unless you can get it to work opposite the belt tension.

1) After lining up the TDC mark on the crank pulley/ dampener (be exact), use a medium sized c-clamp in the *starter opening to hold the flywheel when changing the timing belt on a car with automatic (or a manual). This should just fit in the starter opening & be oriented in the direction of flywheel travel so the back of the clamp takes the load; clamp it solidly back in BEHIND the ring gear. Holds real well and makes sure the crank STAYS NEAR TDC during the whole job and the removal of the crank pulley/ dampener.

*After disconnecting the battery, remove the starter by backing out the (2) bolts and letting it hang on some coat-hanger wire and the heavy positive wire. No need to remove anything else.


2) The crank damper/pulley is machined from brittle cast iron and will likely chip if pried on too much. Just remove 2 or 3 bolts and use 2 or 3, 1 1/2" to 2" 6mm bolts and a steering wheel puller to remove the pulley/damper as a unit. Some might not have the holes.

*If the crank gear is stuck, the best method is probably to drill (2) 1/4-20 holes in it on opposite sides and use a puller...but you might start by trying to pry it off and possibly use a *crows-foot puller on it. When using pullers on the end of the crank, you need to be very careful not to mess up the threads in the end of it or any part of the crank surface...push against the large bolt head only.

* a cheapo puller can have the "feet" ground down quite a bit in order to just catch the edges of the crank gear...you can also use a large hose clamp to keep them on the gear while pulling it.

3) To loosen the cam gear bolts, be sure the OLD belt is reasonably tight by readjusting the tensioner. It's best to ALSO use a heavy screwdriver or prybar to hold the gear vs the head as well as using the belt. The same method is used to tighten the cam gears to specs, using the OLD belt & prybar again. C-clamp still holds the flywheel.

4) One part that SHOULD be replaced while doing the T-belt is the small right angle *hose between the heads at the front. This hose deals with a lot of heat and mine was seriously "rotten", i. e., rubber & cord could easily be torn by hand. Same with the 4" diaaeter hose. While messing in this area, it's probably best to replace the several gaskets in here also.

*Look for any coolant leakage in this area BEFORE the car is FIRST torn down using a flashlight.

There are also 2 bolts that look like they thread into coolant and can leak; they will need the threads gooped.

*I tested all old coolant hoses by slitting them with a knife and attempting to rip them by hand. The only other hose that was weak (other than the small elbow) was the short 4" full diameter hose right at the front.

5) I'd recommend using very light coats of Permatex non-permanent gasket sealer on both sides of any coolant gaskets that are replaced. Real cheap insurance. Clean ALL old gasket or goop off the surfaces first with a dull blade. Use a little moly grease on any bolt threads not going into coolant.

*In order to easily see the gear alignments, take a small brush and some quick-drying paint from a spray can, and after cleaning with lacquer thinner; MARK the punch marks on both the 3 gears and the backing plates/oil pump housing. This way, if anything moves, it will be easily seen. You also need to be aware of the parallax effect where you'll find that if you don't look straight at something when you check it's alignment, you can be pretty far off...use a small mirror if you have to.

6) Be careful when removing the old cam/crank seals. They can be difficult and you DON'T want to scratch the camshaft surfaces where the seal rides OR even the soft aluminum bore that the seal fits into. I used a medium sized flat screwdriver resting on the camshaft/crankshaft in FRONT of where the seal rides on it...you could wrap some tape on this or use some alum flashing to avoid scratching the outer shaft surface.

To install, you need to coat the rubber seal surfaces with grease and I use a little nonpermanent Permatex sealer on the outside of each seal where they press into the oil pump or heads. Will have to make something to tap the seals in straight till they are flush with the front surface, since you don't want to start them in "sideways" at all, I used some PVC tubing of the right diameter and with ends sanded square (90 degrees vs length).

* A thin film of moly grease or anti-seize should be used on the crankshaft where the cam gear goes due to potential rusting & seizure. A new Nissan key also, along with a good (or a new) plate at the back of the gear. Also a good idea to check carefully, the edges of all cam gears for burrs and dress these down with a small stone or file (by hand only) if needed.

Installing the new belt:

1) This is the last thing you do before you put the cover on and the rest back together…be sure everything is done, seals in, gears on, waterpump, CHTS, hoses, gaskets, everything cleaned, etc…. DONE RIGHT…. before proceeding.

2) Recheck the cam gear's alignment with the mark on the oil pump housing…same with the cam gears vs the backing plate marks. Be exact here. BE SURE THE CAM GEAR IS EXACTLY ON THE MARK....

3) The belt should have the arrow facing the front. It is the alignment of the 3 gears and their respective backing marks in this static position that COUNTS…this process aligns the engine, the belt keeps this alignment during rotation.

4) You need to put some reasonable tension on the new belt to check the alignment for the 1st time. Then, look at the crank gear again and check / adjust it if needed, then look at the cam gears vs the backing plate marks.

** IF you can move either cam gear one tooth vs the belt and be able to IMPROVE the alignment vs the backing plate for either cam gear…….DO IT. If you can't…it is aligned?


Verification....

· The 3 lines on the belt SHOULD confirm the backing plate alignment, with the line on the crank gear mark and the other 2 lines on the cam gear marks (pass side is dotted). There should also be 40 teeth between the (2) cam lines & marks.

· There should be 43 belt teeth between driver side cam dimple and crank gear dimple.

The span (marks & lines and number of teeth between the right cam gear mark & line DOWN TO the crank gear mark & line) on the RIGHT determines your overall valve timing vs the crank; while the 40 teeth AND marks & lines between the cam gears at the TOP makes sure BOTH cams are correctly timed vs the crank gear. The tensioner span on the LEFT basically MAINTAINS the the alignment of the other (2) sides during rotation.

1) I used a paving block and a brick (glued together with silicone caulking) that weighed exactly 22 lbs (according to a baby scale> checked this against PO scale!), glued a stick on one end (notched some to get past the FPR) and using this on the top span, got the tension close to specs. I had some minor belt noise for the first few days, but had little after this.

* It would be very easy to overtighten the belt. Since an overtight belt produces heat, and heat deteriorates rubber & cord, it's not a good idea. Not to mention the excess load on the tensioner & camshafts...DON"T DO IT!

* I'd recommend leaving the tensioner spring out of the mix, if you can't get it to exert tension opposite the belt, forget rotating the engine, and doing the feeler gauge baloney. If you've kept everything lined up and the engine ran before, you don't need to do all this.

* The use of the weight might seem a little dufus (hey, he's just using gravity!), but if you are doing the job alone, it is relatively easy to just balance the weight and get the right deflection vs a straight edge, since you don't need to also keep the tension correct as with a fish scale. And some say that fish scales are not accurate.

2) Torque the tensioner to specs and REDO number (4) above to verify that you have the gears aligned right...being sure to check the EXACT crank gear alignment FIRST.

3) You are almost done.



Post Edited (May 15, 3:38am)
 
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